The preparation of block copolymers of mono alkenyl arenes and conjugated dienes is well known. One of the first patents on linear ABA block copolymers made with styrene and butadiene is U.S. Pat. No. 3,149,182. These polymers, in turn, could be hydrogenated to form more stable block copolymers, such as those described, for example, in U.S. Pat. No. 3,595,942 and U.S. Reexamination No. 27,145. Such polymers are broadly termed ‘Styrenic Block Copolymers’ or SBC's.
SBC's have a long history of use as adhesives, sealants and gels. A recent example of such a gel can be found, for example, in U.S. Pat. No. 5,879,694. With the increased use of oil gels, the need for improved properties (expressed in terms of higher tensile strength and higher elongation) exist. Such gels may also be used, for example, as a water proofing encapsulant/sealant for electronics and in wire and cable applications.
An anionic block copolymer based on mono alkenyl arene end blocks and a controlled distribution mid block of a mono alkenyl arene and a conjugated diene has been discovered and is described in copending and commonly assigned U.S. patent application Ser. No. 10/359,981, filed Feb. 6, 2003 and entitled “NOVEL BLOCK COPOLYMERS AND METHOD FOR MAKING SAME”. Methods for making such polymers are described in detail in the above-mentioned patent application.
Copending and commonly assigned U.S. patent application Ser. No. 10/359,462 filed Feb. 6, 2003 and Ser.No. 10/745,352 filed Dec. 22, 2003, both entitled “GELS FROM CONTROLLED DISTRIBUTION BLOCK COPOLYMERS” describe gel compositions that include the anionic block copolymer of the '981 application and a mineral oil such as, for example, a petroleum-based white oil. Examples of such petroleum-based oils include paraffinic oil and naphthenic oil. It is reported in the '462 and the '352 applications that such gel compositions have improved properties including, for example, a high softening point and melt viscosity, as compared to gel compositions that include conventional hydrogenated anionic block copolymers.
Although improved gel compositions are disclosed in the '462 and '352 applications, those gel compositions use mineral oils that are not considered to be environmentally friendly. There is thus an interest in gelling natural product oils, such as soybean oil, because the natural product oils are considered to be more environmentally friendly. One problem with using natural product oils in the preparation of gel compositions is that such oils are not always compatible with the polymer it is being gelled with. For example, natural product oils are too polar to be used with most conventional anionic block copolymers.
It has now been surprisingly discovered by the present applicant that the anionic block copolymers of the '981 application are compatible with natural product oils such as, for example, soybean oil and other like ester compounds, and that substantially clear blends, which do not exhibit any significant oil bleed can be formulated.